Nuclear transfer and cell transplantation: Making more with less

Pig cloning can be achieved by transfer of nuclei of differentiated somatic cells into enucleated oocytes. Then, developing embryos are placed into su rrogate mothers for further development to full term. Although cloned pigs offer the possibility of unlimited organ supply for compatible xenotranspla ntation in humans, the yield of a predictable number of offspring is stili at an experimental phase. Spermatogonial stem cells from a fertile donor ca n be transplanted to the testes of infertile recipients and generate sperm. At present, results from xenogeneic spermatogenesis by transplantation ind icate that porcine, bovine and equine spermatogonia find the interior of th e seminiferous tubular environment not favorable for further differentiatio n into meiotic prophase spermatocytes, Spermatogenic cell transplantation i s a promising experimental alternative for understanding the conditions req uired by both the donor cells and the recipient testis to coexist and even cooperate towards the full development of fertilizing sperm. Mel. Reprod. D ev. 57:211-213, 2000. (C) 2000 Wiley-Liss, Inc.